FIG. 1 (Prior Art) is a circuit diagram of a system of ordinary electric incandescent lamps or light bulbs 1-6 such as might be found in a building. A pair of conductors 7 and 8 extends into a wall box 9. These conductors are designated as the AC live conductor 7 (also referred to as the AC line conductor) and an AC neutral conductor 8. This pair of conductors is usually sheathed together in a common insulator where it extends through the walls of the building. A second set of conductors 10 and 11 extends from the wall box to the electric lamps (also commonly referred to as “lights”). The conductors 7, 8, 10 and 11 generally represent an installed wiring infrastructure of the building. These conductors are embedded in walls and ceilings and are difficult to replace or modify.
A dimmer switch 12 is provided in the wall box. Dimmer switch 12 includes a manual paddle switch 13 (also referred to as a rocker switch) that can be manipulated by a person to turn off and to turn on the lights. Dimmer switch 12 also includes a slider 14 (using a sliding adjustable resistor) that can be manipulated by a person to adjust the brightness of the lights. Dimmer switch 12 has terminals 15 and 16 for connecting the dimmer switch to conductors 10 and 7, respectively. In the illustrated example the terminals 15 and 16 are wires but in other examples the terminals 15 and 16 may be screw clamping mechanisms or insertion fit mechanisms. Terminal 15 is connected to conductor 10 via twist-on wire connector 18. Terminal 16 is connected to conductor 7 via twist-on connector 17. A third twist-on wire connector 19 connects the neutral conductor 8 to the neutral conductor 11 extending to the lights. The dimmer switch is of a form factor that fits into, and attaches to, the wall box 9. A face plate 20 is secured over the installed dimmer switch.
Such dimmer switches typically involve a bidirectional AC switch such as a TRIAC (triode for alternating current) that can selectively break and make the AC live connection that extends to the lights. If the lights are to be off, then the TRIAC is controlled to be nonconductive such that the AC live connection to the lights is broken. AC power to the lights is cut and the lights are not on. If the lights are to be on, then the TRIAC is controlled to be conductive. The AC live connection to the lights is in tact, AC power flows to the lights, and the lights are on.
If the lights are to be dimmed, however, then the TRIAC is made to be nonconductive during only a portion of each cycle of the AC signal. Typically, the TRIAC is controlled to be off starting at the time when the AC power signal is at zero degrees in its sinusoidal wave. At the time of zero degrees, the voltage between conductors 7 and 8 is zero volts. The TRIAC is controlled to remain off for an amount of time as the voltage between conductors 7 and 8 increases from zero volts. The voltage difference between conductors 7 and 8 increases, but due to TRIAC being nonconductive the AC live connection to the lights is broken and power does not flow to the lights during this time. Then at some period of time later, the TRIAC is controlled to be conductive. The AC power connection to the lights is reestablished. This condition persists with power flowing to the lights until the phase of the AC power signal on conductors 7 and 8 reaches one hundred eighty 180 degrees. At this point the voltage between the conductors 7 and 8 is decreasing and crosses zero volts again. The TRIAC is controlled to turn off and to remain off for an amount of time as the voltage between conductors 7 and 8 goes negative. Then at some period of time later, the TRIAC is controlled to be conductive so that the AC power connection to the lights is reestablished.
In this way, the TRIAC is made to break the AC electrical circuit to the lights during portions of time following the zero-crossings of the AC power signal at zero degrees and at one hundred eighty degrees. The overall amount of energy supplied to the lights over the time of a cycle of the AC power signal depends on how long the TRIAC remains nonconductive following these zero-crossings. The longer the times, the less energy is supplied to the lights over the cycle, and the dimmer the lights are. The shorter the times, the more energy is supplied to the lights over the cycle, and the brighter the lights are. By manipulating slider 14, a person can adjust the times, and thereby adjust the proportion of the AC power cycle that the TRIAC is nonconductive, and thereby adjust the brightness of the lights. Such a dimmer switch typically includes a microcontroller that detects the zero-crossings of the AC power signal, that detects the position of the paddle switch 13 and the slider 14, and that controls the TRIAC accordingly. Ways of improving the functionality of the conventional lighting system in ways that exploit the already installed wiring infrastructure are desired.